Jon busts a few myths in this month's grower tech article

I’m sure we have all been subject to (or have even contributed to) horticultural myths and misunderstandings from time to time.  In most cases, information has been given with the best of intentions but critical information is either left out or not understood well enough.  Sometimes it is just confusion over a similar sounding word that can create a problem.  I will try to outline a few examples below.

• Myth 1 - Alkaline water and Alkalinity of water are the same thing – answer: NO

When we refer to alkaline water, we are really describing the pH of the water – alkaline being above a pH of 7.  When we refer to the alkalinity of water, we are describing the water’s ability to neutralise acids - mainly due to the amount of bicarbonates and carbonates it contains.

• Myth 2 - Lower pH water will be easier to acidify than higher pH water – answer: NOT NECESSARILY

I came across a very good example of this recently!  Grower A had water tested and the pH was found to be 9.3.  Grower B had water tested and the pH was found to be 8.3.  Both growers wanted to achieve a target water pH of 5.8.  Despite the fact that Grower B’s water was a whole pH unit lower than Grower A’s, the acid required to reduce the pH to 5.8 was more than four times the volume that Grower A required!  Why? - because Grower B’s alkalinity (310ppm CaCO₃) was more than four times higher than Grower A’s (71ppm CaCO₃)!  In other words, Grower A’s water had less neutralising ability and a little acid went a long way.

• Myth 3 – Phosphite is a plant nutrient – answer: NO

This is a very common misunderstanding (and sometimes misused for marketing purposes!).  Phosphates certainly are plant nutrients but phosphites have no nutritional value!  Phosphites are commonly derived from phosphorous acid (not phosphoric acid) contained in such products as Phosgard™ and Foschek™ etc etc.  They have excellent fungicidal properties but experiments have shown that hydroponically-grown plants fed with phosphites as the sole source of P, performed badly and showed P-deficiency symptoms.

The above are just a few examples of common misunderstandings that exist in our industry.  They highlight the need for clearer and more detailed understanding of some critical topics before correct decisions can be made.